From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Quadros Subject: Re: [PATCH v7 10/14] usb: otg: add hcd companion support Date: Thu, 12 May 2016 11:34:04 +0300 Message-ID: <57343FFC.9090105@ti.com> References: <57333DFF.3090609@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Yoshihiro Shimoda , Alan Stern , Rob Herring Cc: "peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org" , "balbi-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org" , "dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "jun.li-KZfg59tc24xl57MIdRCFDg@public.gmane.org" , "mathias.nyman-VuQAYsv1563Yd54FQh9/CA@public.gmane.org" , "tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org" , "Joao.Pinto-HKixBCOQz3hWk0Htik3J/w@public.gmane.org" , "abrestic-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org" , "linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-omap@vger.kernel.org On 12/05/16 07:00, Yoshihiro Shimoda wrote: > Hi, > >> From: Alan Stern >> Sent: Wednesday, May 11, 2016 11:47 PM >> >> On Wed, 11 May 2016, Roger Quadros wrote: >> >>>> What I mean is if you have 2 EHCI controllers with 2 companion >>>> controllers, don't you need to know which companion goes with which EHCI >>>> controller? Just like you do for the otg-controller property. >>>> >>> >>> That is a very good point. I'm not very sure and it seems that current code won't work >>> with multiple EHCI + companion instances. > > I may misunderstand this topic, but if I use the following environment, it works correctly. > > < My environment > > - an otg controller: Sets hcd-needs-companion. > - ehci0 and ohci0 and a function: They connect to the otg controller using "otg-controller" property. > - ehci1 and ohci1: No "otg-controller" property. > - ehci2 and ohci2: No "otg-controller" property. > > In this environment, all hosts works correctly. > Also I think if we have 2 otg controlelrs, it should be work because otg_dev instance differs. The topic is about more than one otg controllers and how to tie the right ehci and ohci to the correct otg_dev instance especially in cases where we can't depend on probe order. > Or, does this topic assume an otg controller handles 2 EHCI controllers? > I'm not sure such environment actually exists. No it is not about that. > >>> Alan, does USB core even know which EHCI and OHCI are linked to the same port >>> or the handoff is software transparent? >> >> The core knows. It doesn't use the information for a whole lot of >> things, but it does use it in a couple of places. Search for >> "companion" in core/hcd-pci.c and you'll see. > > Thank you for the information. I didn't know this code. > If my understanding is correct, the core/hcd-pci.c code will not be used by non-PCI devices. That is correct. > In other words, nobody sets "hcd->self.hs_companion" if we use such a device. > So, I will try to add such a code if needed. I think OTG core would have to rely on USB core in providing the right companion device, just like we rely on it for the primary vs shared HCD case. cheers, -roger -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752669AbcELIeZ (ORCPT ); Thu, 12 May 2016 04:34:25 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:58202 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752569AbcELIeW (ORCPT ); Thu, 12 May 2016 04:34:22 -0400 Subject: Re: [PATCH v7 10/14] usb: otg: add hcd companion support To: Yoshihiro Shimoda , Alan Stern , Rob Herring References: <57333DFF.3090609@ti.com> CC: "peter.chen@freescale.com" , "balbi@kernel.org" , "gregkh@linuxfoundation.org" , "dan.j.williams@intel.com" , "jun.li@freescale.com" , "mathias.nyman@linux.intel.com" , "tony@atomide.com" , "Joao.Pinto@synopsys.com" , "abrestic@chromium.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-omap@vger.kernel.org" , "devicetree@vger.kernel.org" From: Roger Quadros Message-ID: <57343FFC.9090105@ti.com> Date: Thu, 12 May 2016 11:34:04 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/05/16 07:00, Yoshihiro Shimoda wrote: > Hi, > >> From: Alan Stern >> Sent: Wednesday, May 11, 2016 11:47 PM >> >> On Wed, 11 May 2016, Roger Quadros wrote: >> >>>> What I mean is if you have 2 EHCI controllers with 2 companion >>>> controllers, don't you need to know which companion goes with which EHCI >>>> controller? Just like you do for the otg-controller property. >>>> >>> >>> That is a very good point. I'm not very sure and it seems that current code won't work >>> with multiple EHCI + companion instances. > > I may misunderstand this topic, but if I use the following environment, it works correctly. > > < My environment > > - an otg controller: Sets hcd-needs-companion. > - ehci0 and ohci0 and a function: They connect to the otg controller using "otg-controller" property. > - ehci1 and ohci1: No "otg-controller" property. > - ehci2 and ohci2: No "otg-controller" property. > > In this environment, all hosts works correctly. > Also I think if we have 2 otg controlelrs, it should be work because otg_dev instance differs. The topic is about more than one otg controllers and how to tie the right ehci and ohci to the correct otg_dev instance especially in cases where we can't depend on probe order. > Or, does this topic assume an otg controller handles 2 EHCI controllers? > I'm not sure such environment actually exists. No it is not about that. > >>> Alan, does USB core even know which EHCI and OHCI are linked to the same port >>> or the handoff is software transparent? >> >> The core knows. It doesn't use the information for a whole lot of >> things, but it does use it in a couple of places. Search for >> "companion" in core/hcd-pci.c and you'll see. > > Thank you for the information. I didn't know this code. > If my understanding is correct, the core/hcd-pci.c code will not be used by non-PCI devices. That is correct. > In other words, nobody sets "hcd->self.hs_companion" if we use such a device. > So, I will try to add such a code if needed. I think OTG core would have to rely on USB core in providing the right companion device, just like we rely on it for the primary vs shared HCD case. cheers, -roger